In a twisting apparatus a yarn package or a plurality of yarn packages is mounted on a hollow spindle often provided with an internal thread brake. This spindle is normally rotatable with a flyer disk underlying the yarn packages. One or more yarns is pulled off the packages upwardly and is then passed downwardly through the hollow spindle, past the thread brake, and out a lateral hole in the rotating flyer. Thereafter the filament passes several times around the flyer reservoir disk and moves upwardly around the yarn packages forming a so-called balloon within an upwardly extending sleeve spaced laterally outwardly from the yarn packages. Thus each yarn or other filament must pass axially upwardly, radially inwardly, axially downwardly, radially outwardly, and axially upwardly again. (See German Offenlegungsschrift DT-OS No. 23 09 578.)
Obviously, threading a filament along such a complicated path is a complicated operation, and to this end pneumatic threaders have been employed. Normally these are simple blow guns of the standard commercially available type. The end of the filament is poked into the upper end of the inlet tube on the top of the twister, this tube is depressed as described in the above-cited application Ser. No. 725,494 in order to clear the passage through the inlet tube, and a blast of air is fired down the inlet tube. This air normally entrains the filament down along the relativey complicated path and even upwardly out of the annular upwardly open balloon gap.
There are three main problems with this system. Firstly, a common occurrence is that the filament gets pinched between the blow gun and the inlet tube so that it cannot flow freely. Secondly, this operation normally requires th operator to hold the blow gun in one hand and depress the inlet tube with the other so that the probability of of the yarn falling out of the inlet tube or of the operator blowing the yarn away from the inlet tube is considerable. Finally this system, when it works, is often so very powerful that several meters of the filament are blown up out of the balloon gap before the operator has time to release the trigger on the blow gun or grasp the filament. Thus this last-given disadvantage is particularly troublesome in systems where the twisters are arranged in banks, so that the loose filament can catch in other twisters and create a tangle that must be painstakingly removed.